US11550983B2ActiveUtilityPatentIndex 47
Method for determining an electrical model of a string of photovoltaic modules, diagnostic method and device associated therewith
Assignee: COMMISSARIAT ENERGIE ATOMIQUEPriority: Nov 14, 2018Filed: Nov 13, 2019Granted: Jan 10, 2023
Est. expiryNov 14, 2038(~12.4 yrs left)· nominal 20-yr term from priority
Inventors:LESPINATS SYLVAIN
Y02E10/50G06F 2111/10G06F 30/367H02S 50/10G06F 30/00G06F 30/38G06F 2119/06
47
PatentIndex Score
0
Cited by
13
References
10
Claims
Abstract
A method for determining an electrical model of a string of photovoltaic modules from a characteristic I(V) of the string includes detecting a first linear zone and a second linear zone of the characteristic I(V); initialising the parameters of a non-by-pass electrical model corresponding to a first operating condition, called a non-by-pass condition; optimising the parameters of the non-by-pass electrical model from a reference characteristic I(V ref ) equal to I(V), determining the parameters of the electrical model corresponding to a second operating condition, called a by-pass condition, in order to obtain a by-pass electrical model from the characteristic determining, from the characteristic I(V) the best model among the non-by-pass model and the by-pass model.
Claims
exact text as granted — not AI-modifiedThe invention claimed is:
1. A method for determining an electrical model of a string of photovoltaic modules from a characteristic I-V of said string and a non-by-pass model corresponding to a first operating condition of the string, called a non-by-pass condition, given by the following equation:
Y
=
I
p
h
-
W
t
h
+
R
s
×
Y
R
p
-
I
0
×
(
e
W
t
h
+
R
s
×
Y
N
-
1
)
with I ph the photocurrent, R s the series resistance, R p the parallel resistance, I 0 the dark current of the diode,
N
=
k
q
×
N
s
×
T
ideal
with T ideal ∈[200,300], N s the number of series cells in the string, k b is the Boltzmann's constant and q is the elementary charge of a proton, Y the current passing through the string and W th the voltage across the string, I ph , R s , R p , I 0 and N being parameters of the non-by-pass model; and a by-pass model corresponding to a second operating condition of the string, called a by-pass condition and given by the following equation:
W mod ( Y )= W 1 ( Y )+ W 2 ( Y )
with W mod the voltage across the string according to the by-pass model for the current Y,
W
1
(
Y
)
=
(
1
-
P
d
)
×
W
t
h
(
Y
)
and
W
2
(
Y
)
=
P
d
×
W
t
h
(
Y
1
-
P
I
)
where W th (Y) is the voltage across the string given by the non-by-pass model, P d the by-pass diode proportion and P I the short-circuit current loss proportion induced by the by-pass, Pa and Pi being parameters of the by-pass model, the method comprising:
a step of detecting a first linear zone and a second linear zone of the characteristic I-V;
a step of initialising the parameters of the non-by-pass electrical model from the characteristic I-V;
a step of optimising the parameters of the non-by-pass electrical model from a reference characteristic I(V ref ) equal to I(V);
a step of determining the parameters of the by-pass electrical model, in order to obtain a by-pass electrical model from the characteristic I-V; and
a step of determining, from the characteristic I-V, a best model from the non-by-pass model and the by-pass model.
2. The method according to claim 1 , further comprising, before the step of detecting the linear zones of the characteristic I-V, a step of checking the data of the characteristic I-V.
3. The method according to claim 2 , wherein the step of checking the data of the characteristic I-V comprises at least one of both following sub-steps:
a sub-step of detecting the switching period of the string, the data measured outside the switching period being removed;
a sub-step of removing the outliers.
4. The method according to claim 1 , wherein the step of detecting a first linear zone and a second linear zone of the characteristic I-V comprises:
a sub-step of determining the maximum power point (I MPP , V MPP ), the points of the characteristic I-V located above the straight line passing through the origin (0,0) and the point (I MPP , V MPP ) being considered as candidates for the first linear zone, and the points located below this straight line being considered as candidates for the second linear zone;
a sub-step of determining the linear model of the current Y as a function of the voltage W across the string such that Y=a sc ×W+b sc from the candidate points for the first linear zone and the linear model of the voltage W across the string as a function of the current Y such that W=a oc ×Y+b oc from the candidate points for the second linear zone, so as to determine the parameters a sc , b sc , a oc and b oc .
5. The method according to claim 4 , wherein during the step of initialising the parameters of the non-by-pass electrical model, the parameters of the electrical model I ph , R s , R p , I 0 and N are initialised in the following way:
R p is given by
R
p
=
-
1
a
sc
;
N is given by
N
=
k
q
×
N
s
×
T
ideal
with T ideal ∈[200,300];
I 0 is given by
I
0
=
R
p
×
b
sc
-
b
oc
R
p
(
e
b
oc
N
-
1
)
;
R s is given by
R
s
=
-
a
oc
-
N
×
R
p
N
+
l
0
×
R
p
×
e
b
oc
N
;
and
I ph is given by
I
ph
=
R
p
+
R
s
R
p
×
b
sc
+
I
0
×
(
e
R
s
×
b
sc
N
-
1
)
.
6. The method according to claim 1 , wherein the model comprises a linear component and an exponential component and in that the step of optimising the parameters of the non-by-pass electrical model comprises:
a first sub-step of optimising the parameters of the linear component of the non-by-pass electrical model comprising:
a phase of determining a linear characteristic so as to obtain I linear (V);
a phase of determining the linear regression of the equation Y=a sc ×W+b sc from the curve I linear (V);
a phase of determining the parameters of the linear component of the model from said regression;
a second sub-step of optimising the parameters of the exponential component of the non-by-pass electrical model comprising:
a phase of determining a linear characteristic V-I so as to obtain V linear (I);
a phase of determining the linear regression of the equation W=a oc ×Y+b oc from the curve V linear (I);
a phase of determining the parameters of the exponential component of the model from said regression;
said first and second sub-steps being iterated a plurality of times so as to obtain a non-by-pass electrical model.
7. The method according to claim 1 , wherein the step of determining the parameters of the by-pass electrical model comprises:
a first sub-step of initialising the first parameter P d and the second parameter P I which are characteristic of the by-pass;
a second sub-step of determining, from the parameters P d and P I , the characteristic W mod (Y) associated with the by-pass model;
a third sub-step of optimising the parameters P d and P I of the by-pass model W mod (I);
a fourth sub-step of deforming, from the parameters P d and P I , the curve I(V) so as to obtain a non-by-pass characteristic I(V unshaded );
a fifth sub-step of optimising the parameters of the non-by-pass electrical model from a reference characteristic I(V ref ) equal to I(V unshaded );
the second, third, fourth and fifth sub-steps being iterated a plurality of times so as to obtain a by-pass electrical model from the non-by-pass model re-evaluated and the parameters P d and P I .
8. A method for detecting an anomaly in a string of photovoltaic modules, comprising:
a step of determining the electrical model of the string of modules using a method according to claim 1 ;
a step of detecting an anomaly as a function of the value of at least one parameter of the electrical model determined.
9. A data processing device comprising a system for implementing the method according to claim 1 .
10. A non-transitory computer readable medium comprising machine executable instructions which, when the program is run on a computer, cause the computer to implement the method according to claim 1 .Cited by (0)
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